The present invention relates generally to driveshafts and their manufacture, and more particularly to driveshafts for use in struts of a ram air turbines (RATs) and their method of manufacture.
Modern aircraft often include a secondary or emergency power system that can provide power in the event that power is unavailable from a primary power system. RATs are commonly used for secondary or emergency power systems to provide electrical and/or hydraulic power. A typical RAT is deployable in flight by opening suitable doors or hatches in the aircraft's fuselage. The RAT presents a rotatable turbine to oncoming airflow, which rotates the turbine. Rotational energy (torque) from the turbine is then transmitted to a suitable power conversion device (e.g., generator, pump, etc.) that converts that rotational energy to a desired form for use by the aircraft. The RAT may include suitable gearing to adjust the rotational energy to a speed suitable for the power conversion device, as well as other drivetrain components that transmit rotational energy (torque) to desired locations.
Driveshafts used in RAT drivetrains are subject to many requirements. The RAT driveshaft must be reliable, it must be able to mate with necessary drivetrain components and it must be able handle the torque loads to which it will be subjected. Due to the fact that most RATs protrude outward from an aircraft's fuselage in a cantilevered manner, RATs and their subcomponents are subject to a significant amount of vibration and bending. Moreover, the rotational nature of RAT drivetrains can introduce torsional resonance issues. However, because positioning of the RAT in the aircraft must account for numerous other aircraft design factors, the location of the RAT and its subcomponents is highly constrained, which greatly limits design options for the geometry and dimensions of the RAT drivetrain and its driveshafts.